This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. ABSTRACT Biliary atresia is the most common cause of cholestasis in infants and the most frequent indication for pediatric liver transplantation. The disease results from a destructive inflammatory process that affects intra- and extrahepatic bile ducts, leading to fibrosis and obliteration of the biliary tract. Although little is known about the etiology or pathogenesis of biliary atresia, epidemiologic and virologic studies point to a complex trait disorder, in which environmental factors trigger an inflammatory process that recognizes and abnormally targets the biliary system during a specific phase of postnatal development. Based on these data, the following unifying pathogenesis model can be preliminarily proposed: Regardless of initiating (environmental) and modifying (genetic) factors for disease development, the inflammatory and fibrosing destruction of the biliary epithelium is common to all clinical forms of biliary atresia. In this setting, the potential decrease of this inflammatory component by corticosteroid treatment may result in improved bile flow and better outcome after portoenterostomy. Therefore, in this clinical trial we propose to objectively determine whether corticosteroid treatment improves bile flow in infants with biliary atresia. The significance of the proposed trial is that it will determine whether corticosteroids are an effective medical treatment to improve bile drainage and long-term outcome, and whether its use reduces the need for liver transplantation in infants with biliary atresia. The trial will be performed by the NIH-supported Biliary Atresia Research Consortium (BARC). BARC has the infrastructure to prospectively follow a sufficiently large number of patients and to collect samples necessary for clinical research studies addressing etiology, pathogenesis, diagnosis, and treatment of children with biliary atresia.